


You're My Mortal Flaw, and I'm Your Fatal Sin

by BlackRoseShiori



Series: Supernatural Oneshots [3]
Category: Supernatural
Genre: Angst, Angst and Fluff and Smut, Bisexual Dean Winchester, Bottom Castiel/Top Dean Winchester, Canon Temporary Character Death, Castiel/Dean Winchester First Kiss, Dean Winchester is incapable of using his words, Destiel - Freeform, Emotional Hurt/Comfort, Episode: s12e10 Lily Sunder Has Some Regrets, Episode: s12e12 Stuck In The Middle (With You), Episode: s12e23 All Along the Watchtower, First Time, Idiots in Love, M/M, Mentions of Ishim, Mentions of Lily Sunder, POV Alternating, Protective Dean Winchester, mention of alcoholism
Language: English
Status: Completed
Published: 2021-02-15
Updated: 2021-02-15
Packaged: 2021-03-14 20:20:26
Rating: Explicit
Warnings: Graphic Depictions Of Violence, Major Character Death
Chapters: 1
Words: 3,834
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29052030
Author URL: https://archiveofourown.org/users/BlackRoseShiori/pseuds/BlackRoseShiori
Summary: Dean could have lost Cas to a revenge-driven angel hunter, and almost did lose him to a crazy rogue angel.And if that wasn't bad enough, he almost lost Casagainbecause of a Prince of Hell and the Lance of Michael.Enough was, finally, enough.
Relationships: Castiel & Dean Winchester & Sam Winchester, Castiel/Dean Winchester
Series: Supernatural Oneshots [3]
Series URL: https://archiveofourown.org/series/2084058
Kudos: 20





	You're My Mortal Flaw, and I'm Your Fatal Sin

**Author's Note:**

> I've been re-watching the show since it ended, and I recently finished season 12 again, and I enjoyed it a lot more than I remembered. 'Lily Sunder Has Some Regrets' and 'Stuck in the Middle (With You)' are easily two of my favorite episodes. There's the mythos of a human able to use angel magic, meeting the delightfully deranged Ishim, and then like two episodes later we meet another Prince of Hell and see the Lance of Michael in the flesh, and Cas almost bites it both times. It's a lot! Season 12 didn't have to go that hard! 
> 
> So, basically, Dean is sick of this shit.
> 
> Mind the tags for some 'All Along the Watchtower' angst, but you've been there and seen it before.
> 
> Happy Destiel Wedding Day! Here's some porn I just finished. You're welcome.

_"My memory refused  
To separate the lies from truth  
And search the past  
My mind created_

_I kept on pushing through  
Standing resolute, which you  
In equal measure  
Loved and hated..."_

-Beth Crowley, Warrior  


* * *

  


It was a shitty motel room, not terribly different than all the others. There were two full-sized beds, ugly green comforters, and one nightstand between them.

The only difference between this room and many of the others was the absence of one younger brother, and the presence of one moping, fallen Angel of the Lord.

"Cas, we need to talk."

Castiel's head whipped up from where he'd been sitting, perched on the edge of the bed closest to the door, reading something on Sam's tablet.

"Of course, Dean."

He sat the tablet face down on the bed and waited as Dean closed and locked the door behind him.

Dean fidgeted a bit, shifting his weight from foot to foot, until finally walking over to sit next to Cas.

Dean's head hung down, his hands were clenched into fists, and his eyes were fixed on the filthy carpet when he said, "You almost died today." 

"That's true," Cas replied, matter-of-fact.

Dean sighed and threw his head back, glaring up at the popcorn ceiling like it had personally offended him.

Cas waited patiently for Dean to speak again.

"That can't happen again."

This time, Cas sighed. "Dean, you know how these things go. I can't promise not to almost die, and neither can you. It would be a promise that none of us could keep. Not just the two of us, but also Sam, Mary, or any hunter."

Dean frowned, trying to find the words. 

"You're not just any hunter," is what he finally settled on.

Cas huffed an annoyed breath of air out of his nose, which he only did when he was reaching the end of his patience; usually with Dean. In fact, almost exclusively with Dean.

"Dean," Cas began, in a tone more gentle than usual, "I'm actually safer than most. I can usually heal myself, and others; and even when I can't, there's still a good chance I'll pull through. I'm not without my grace, you know."

Dean ran both hands roughly down his face before finally turning to look Cas in the eyes.

"Other angels can kill you, and we literally just met a human who can use angel magic. So, for all we know, she could have smited you without any weapon at all."

"Smote," Cas interrupted.

Dean frowned. "What?"

Cas' lips turned up at the corners, ever so slightly. "I believe the word you are looking for is 'smote.' She could have smote me without any weapon at all."

Dean blinked at Cas before losing his own internal battle and smiling, just a bit, at the angel.

"You're such a little shit sometimes," Dean said, breaking eye contact and looking down at his lap, where his hands clasped and unclasped nervously.

Cas shrugged, looking more human than ever.

And that, really, was the problem.

"Listen, Cas," Dean continued, looking back up and holding Cas' eyes. "It was seriously just luck that the Lance of Michael didn't poof you out of existence, the way it would a demon. It bought us some time, but only a handful of minutes. If it wasn't for Crowley, who just _happened_ to know the one thing we needed to know to break that spell and cure you, I'd be burning you on a pyre right now. And I can't, man. I just can't."

Castiel held Dean's gaze as he said, "What difference would it make? We had to put Wally on a pyre tonight. Mary had to call his wife. There are always casualties." 

Green eyes narrowed at that, and Dean reached up to grab Cas' left shoulder, which he squeezed just a bit too tight. It was the same shoulder where Cas had once gripped Dean, so long ago, and raised him from perdition. 

Through gritted teeth, Dean said, "The difference is, you're _you_! Damn it, Cas, what about this aren't you getting?"

Castiel squinted at Dean and tilted his head, in a move that was so familiar and just so _Cas_ that it made Dean's heart skip a beat.

Dean just watched the angel for a while, and Cas watched him right back. Of course he did, because this was the part where Cas deferred to Dean. He let Dean make the decisions. He let Dean make the first move. No matter how much Dean screwed up, Cas' trust bordered on blind devotion.

There was so much that Dean would have missed about Cas, if he hadn't made it. Everything from his messy dark hair, the sky blue of his eyes, his stupid trenchcoat (the current one was particularly hideous), and his ugly tie. The way he stood a little too close, and stared a little too hard. All of the times he made them all laugh without really meaning to, although Dean suspected that sometimes it was on purpose, just to get a rise out of them.

Cas always looked at Dean in a way that Dean knew he didn't deserve. A man like him shouldn't be anything to an angel. Cas made mistakes, sure, but his heart was always in the right place. More importantly, he was powerful and ancient, and Dean should have been about as important as an ant to a being like Cas.

He had remade Dean from just a damaged soul. Someone with the power to do that never should have rebelled against heaven for _him._

And yet, here they were.

"Dean?" Cas finally said into the silence that had fallen over them.

Taking a steadying breath, Dean said, "What did Ishim mean, when he said he was going to cure you of your 'human weakness'?"

Cas looked away from Dean, choosing to face the rotting wallpaper across from them, instead. 

Dean dropped his hand from Cas' shoulder and waited.

"It's something that they all say," Cas began, and Dean knew this was going to be hard, given the fact that Cas looked like he was about twenty seconds away from bolting.

"They say things about us. They call me your attack dog, or your slave, or your bitch. Sometimes they mean you Winchesters, plural, but more often than not they just mean you."

He paused, and Dean could see his Adam's apple bob as he swallowed. Dean didn't dare breathe.

"Ishim said what he did because he knows. Demons and angels alike, they know I'll always choose you. Every time, every apocalypse, I will _always_ choose you, Dean."

Dean made his tone remain neutral as he asked, "And why is that?"

Cas finally turned to look at him again, his eyes glistening, and whispered, "Do I really have to say it?"

Dean was moving before his brain even registered what was going on. Which was probably a good thing, because if he'd given himself any kind of warning, he would have probably flung himself out the door instead.

It really wasn't his fault that Cas looked so sincere, so full of love, that Dean wanted to explode with it.

When his lips landed on Cas', the angel didn't immediately kiss him back. He seemed frozen, just for a moment, before he registered what was happening. When he finally started moving his lips against Dean's, it was the eruption of a decade's worth of silent pining and unresolved sexual tension.

Cas pulled Dean even tighter to him, and Dean used that momentum to push Cas down onto the bed. 

With Cas laying flat on his back, Dean swung a leg over the angel's hips and pressed his body as close as he could, so that they were touching nearly everywhere. Cas whimpered into Dean's mouth as he canted his hips up, obviously seeking friction.

Dean grinned a bit when he felt Cas' erection against his hip, but he didn't grind down harder to give the angel any relief. Instead, he breached Cas' lips with his tongue and deepened the ongoing kiss until it was filthy, and Cas seemed to lose all control of his body from the waist down.

After jerking his hips up into nothing for several minutes, Cas finally growled Dean's name between kisses. 

Deciding that he'd teased enough, Dean reached down and placed his palm flat against the bulge in Cas' pants.

Cas pulled away from their excellent make-out session with a gasp.

As Dean looked down at him, Cas' eyes were more black than blue, and he couldn't seem to focus.

Dean grinned.

It had been a while since he'd gotten laid, and even longer since being with a man, but Dean figured it was like riding a bike. Especially when that bike was nearly six feet of beautiful, infuriating angel.

He began running his palm up and down Cas' clothed erection, digging in with the heel of his hand just a bit on the way up. His other hand came around to hold Cas' hip firmly to the mattress.

Dean leaned down to bite at Cas' shoulder, enjoying the aborted little "ah" sounds he was making. In fact, he was enjoying them so much, he captured Cas' mouth again so he could steal those noises from him.

It wasn't long before Cas pulled away again, just enough to speak. Dean watched the angel's eyes, saw the hope and the fear and the desire. 

And the love.

"Dean," was all he said, and that was more than enough.

Dean removed his hand from the angel's cock and sat up, still straddling Cas' hips, to pull his flannel and t-shirt off and fling them somewhere.

Cas seemed to pick up what Dean was putting down, so he bent at the waist enough to shrug out of his trenchcoat and suit jacket. By the time Dean was down to his boxer-briefs, Cas had his tie off but was still struggling with his button-up.

"Let me," Dean said, and his voice sounded foreign to himself. Like whatever was happening at this moment was so important, so monumental, that he would be changed when it was over.

He certainly hoped so.

Dean leaned down and got Cas' shirt unbuttoned and off of him, then reluctantly sat all the way back at the foot of the bed so Cas could shimmy out of his dress pants and kick them off onto the floor.

Now that they were both down to their underwear, Dean leaned back over Cas and slotted their bodies together again. Dean gently, reverently, touched the spot on Cas' abdomen that had been pierced by the Lance of Michael, and rubbed a warm hand over the smooth skin. 

Cas' cock was hard and hot against Dean, so Dean made sure they lined up as he pushed his weight down, which elicited a strangled sound from the angel.

"Can I touch you?" Cas managed to say, "Please."

"Yeah," Dean breathed out, barely audible. 

In the blink of an eye, Cas had flipped them.

Dean's eyes widened in surprise at finding himself on his back, but Cas was already pulling off his underwear, so he figured he could deal with it.

Then Cas' mouth was on Dean's cock, taking him nearly all the way down, and this wasn't what Dean had thought Cas meant by touching, but he was _definitely_ on board.

"Holy shit, Cas!" Dean cried out as the angel hollowed his cheeks and pulled off Dean's cock with a pop.

Cas replaced his mouth with his hand and said, "Was that not adequate?"

Dean gaped at him before saying, "It was more than adequate. Where the hell did you learn to do that?"

Cas shrugged with the shoulder not involved in leisurely stroking Dean's cock. "I do know how to use the internet."

Dean laid his head completely back on the lumpy motel pillow and grinned up at the ceiling. "I love the internet."

Cas rolled his eyes and replaced his hand with his mouth again.

Dean clutched at the angel's dark hair, and Cas moaned around his cock, sending shockwaves through Dean.

Before long, Dean was pulling urgently at Cas' hair, to get him to stop.

Popping off again, looking annoyed, Cas said, "What's wrong?"

"Nothing," Dean assured him. "I just don't want to come yet, and I was well on my way. You're fucking awesome, man."

Castiel's face lit up like a Christmas tree, in a toothy smile that Dean got to see far too rarely.

"You're awesome too, Dean," he said with complete sincerity. It made Dean's heart ache.

"Come here," Dean said, lifting both arms up and toward the angel. He knew he was being a little clingy, but he didn't give a shit.

Cas practically melted into Dean's arms.

Dean placed a soft kiss to Cas' hair, and then gently flipped them again. Now hovering over Cas, Dean said, "I need to know what you want. We could keep using our mouths and hands, and that would be totally fine with me, but if there's anything else you want, you need to let me know."

With a lopsided smile, Cas reached up and pushed a sweaty piece of hair off Dean's forehead. 

"I want everything," he said. "But for right now, what I want most of all is to feel you inside me."

Dean collapsed onto Castiel's chest, pushing his overheated face into the crook of Cas' neck. "You can't just say shit like that, man," he grumbled into the angel's shoulder.

Cas chuckled as he rubbed soothing circles on Dean's back. 

"You did ask."

Dean lifted his head and said, "Okay. This is happening. I've got this. Do you want me to prep you, or can you mojo it? Fair warning: I'm not super experienced with prepping someone else."

Cas tilted his head and squinted at Dean. Dean fought the urge to look away.

"I can do it this time," Cas finally said. "We'll have plenty of time to practice doing it the human way, later."

Dean swallowed thickly. His brain seemed to be stuck on the word _later_ , as if that one word was a prayer. Cas wanted to do this again. _Later._ They had time. Cas planned to stay.

Dean's reverie was broken when Cas said, voice deeper than usual, "I'm ready."

"Okay," Dean said again, before something else occurred to him.

"FUCK! Cas, I don't have lube. For...me. Myself. To help. With the sex."

Cas huffed out a laugh and said, "It's fine, Dean. I'm ready to go."

"Oh," Dean said, feeling like his entire body was on fire. "Good. That's...I'm just gonna...okay."

He took himself in hand and leaned over Cas, capturing his lips in another heated kiss as he simultaneously guided himself to Cas' slick entrance.

Dean pushed in, ever so slowly, because he couldn't stand the thought of hurting Cas again. He had a bad habit of hurting him in other ways, but he desperately wanted to be better. Not just for Cas, but for everyone he loved.

Castiel pulled away with a gasp as Dean pushed his way inside. 

"You okay?" Dean asked, pausing for a moment.

Cas nodded, vigorously, but couldn't seem to find words.

"I'm gonna take that as enthusiastic consent," Dean said with a smirk, and began to move again.

When Dean finally bottomed out, he stayed still to get a grip on himself. He was breathing heavily and was slick with sweat.

"You feel so good," he said through clenched teeth.

Cas was staring up at him with his mouth hanging open.

"Dean," he said, voice thick, "If you don't start moving, I'm going to die."

Dean couldn't help the laugh that escaped him. 

"I doubt that, Sunshine," he said. "Although, we've had some close calls lately, so I'd better make sure you don't die." With that, Dean started to move, setting a comfortable pace that got Cas squirming around underneath him. Dean found that pretty delightful. 

After a few minutes of that, Dean guided Cas' right leg up onto his own shoulder, and bent his left leg over his hip. This gave Dean the opportunity to bend Cas more at the waist, delving even deeper inside the angel, and put Dean in the perfect position to also be able to lean down and press his lips to Cas' and steal some of the little "ah" noises escaping Cas' mouth with each thrust.

Dean was getting close, and Cas was no longer forming words that Dean could understand, other than sometimes his own name. Cas' cock was caught between their bellies, and Dean was so tuned in that he could tell from the swell of the angel's cock, and his attempt to arch his back impossibly more off the bed, that Cas was going to come soon, too.

"That's it," Dean whispered against the angel's lips. "Come for me, Sunshine."

Whether it was the silly pet name, or just the simple demand, Dean didn't know. What he did know was that Cas' eyes flashed the bright silver-blue of his grace, and he made a keening sound that was reminiscent of his true voice as he came between their bodies.

That was all it took to send Dean over the edge. He gave one final, deep thrust, and filled Cas completely.

The bedside lamp exploded.

Sweaty and sticky, Dean collapsed to the side, still breathing heavily.

The room was now completely dark, except for some outside light finding its way past some cracks in the closed curtains. It was also silent, outside of Dean's panting breaths, which were starting to come back down to normal.

Castiel was the one to break the silence.

"Dean," he said, "I don't wish to ruin the moment, but won't Sam be back soon?"

"Oh, shit," Dean said. "I completely forgot I have a brother."

Cas laughed, and it was the most beautiful thing Dean had ever heard.

Cas used his grace to clean them up, but they got re-dressed the human way.

As he was pulling on his tie, Dean surprised Cas by taking his hand and saying, "Hey, we should probably talk more about this..."

He was interrupted by the sound of a key card in the lock.

Dean released Cas' hand a jumped back. Cas ignored the sliver of hurt that went through him.

"Whoa," Sam said, as he walked into the room and let the door close behind him. "Why's it so dark in here?"

"Uh," Dean said, intelligently. "The light broke. Or the bulb blew. Or something."

Sam narrowed his eyes at his brother. Then he turned to look at Cas, who was looking absolutely anywhere else that didn't include a Winchester. 

With a sigh, Sam said, "You know what? I don't even want to know. I'm going to bed."

He walked toward the one that Dean and Cas had just used, but was stopped by Dean launching himself onto it first. 

"This one's mine," he said, doing the patented older sibling starfish pose.

Dean was being seriously weird, even for Dean.

Sam looked at Cas again, and Cas was looking rather pointedly at a rip in the wallpaper.

He sighed again. "Actually, I think I'll shower first. Is that okay with you guys?"

He took their silence as an affirmative.

  


* * *

  


Cas was gone. Really, truly gone. 

Sam had tried to be optimistic. Cas was his friend too, but he knew that Dean needed him to be strong in the wake of this loss. Sam thought that if he could just stay positive and convince Dean that Cas could come back, and their mom could come back, and that maybe they could fix this like they always do...he'd start to believe it, too. 

If he thought about it hard enough, for long enough, or prayed with every fiber of his being, surely Chuck or somebody would do _something_. But the only thing that happened was Jack. 

Dean prepared Cas for his funeral, while Sam took care of Kelly. Sam had started to ask Dean if he wanted to switch, so that Dean wouldn't have to see Cas' body again, but before he could even open his mouth, Dean had looked at him with an expression of such broken rage and sorrow that Sam knew his brother had to be the one to do it. Dean wanted to be the one to touch Cas' empty vessel gently, to wrap him up in sheets and curtains and whatever else was at hand, and he needed to be the one to carry him to the pyre. 

Sam wasn't an idiot. He knew something had recently changed between Cas and Dean. His brother was an outstanding liar, but Sam knew him well enough to know something was up. He'd completely stopped hitting on waitresses, he got a constipated look on his face any time Cas so much as stubbed a toe, and he'd even started drinking less. A little less, anyway, until Cas had up and disappeared with Kelly. 

Sam sighed. He knew that he could kiss sober-Dean goodbye for the foreseeable future. 

As they watched the flames and said some words (there weren't nearly enough words) Sam looked over at his brother. 

Dean's face was worth a thousand words. His eyes were red-rimmed from crying, but beyond that was the expression he wore when he needed to be pointed at something to kill. Sam's stomach dropped. Silent fury rolled off Dean in waves, and that was a very dangerous thing. If Lucifer wasn't already dead ( _please let him be dead_ ) Dean probably would have gone after the sonofabitch with his bare hands; and Sam's money would have been on Dean.

Dean's expression reminded Sam of another time, another pyre. But when Charlie had died, Dean had the Mark of Cain and a singular goal: Murder the entire Styne family. 

This time, there was no one left to kill. Lucifer was already gone.

Sam looked over at Jack.

He knew his brother better than anyone, so he knew who Dean would blame. There was no where else for his fury to go. If Jack hadn't already proven to be basically indestructible, he'd be in grave danger.

Sam knew he'd have to have a difficult talk with his brother, eventually, regarding Jack. But for now, they all needed time to mourn.

As Dean spun on his heel and made his way toward the Impala in silence, Sam knew that something in his brother had been irrevocably broken. 

So Sam let the tears fall. For Cas, for Kelly, for Mary, even for Crowley. 

But as he watched Dean go, he let himself cry for his brother, too. He was already grieving the Dean from yesterday. The Dean before Cas fell to the ground, his broken wings burnt into the dirt around him. The Dean before they watched Mary get dragged back into Apocalypse World with Lucifer. 

They had, for a brief moment, been as close as they'd ever been to happiness.

Sam cried for that loss, too.


End file.
